a) Field of the Invention
The invention is directed to an optical arrangement for obtaining information from a sample or an observed object, with a light source for illuminating the sample or observed object and with a reception device for the light proceeding from the sample or observed object.
b) Description of the Related Art
In optical observation devices such as microscopes it is always necessary to influence the illumination beam path or observation beam path in such a way that optical imaging characteristics are achieved. This applies, for instance, to varying the beam path cross section in the illumination beam path for purposes of optimizing the optical resolution, achieving a high transmission efficiency in the objective, adapting to the objective pupil and correcting the focus volume. Further, it is desirable to be able to vary the imaging scale in the illumination beam path in order to influence the length of an illumination line or change the imaging scale in the observation beam path.
The variable optics known from the prior art for adapting a beam path to an objective are formed, for example, as simple telescopes or cylindrical optics and generally have reflecting and/or refractive optical elements.
Use of refractive optical elements such as those shown in the Figure labeled “Prior Art 1” requires a relatively large build space determined by the sum of the focal lengths of the individual lenses. Further, when using refractive optical elements, steps must be taken to correct chromatic errors if polychromatic light sources are employed; otherwise, the imaging characteristics are not identical for all wavelengths.
The disadvantages mentioned above can be overcome through the use of reflecting elements (shown, for example, in the Figure labeled “Prior Art 2”), but an arrangement of this kind results in imaging errors like astigmatism, for instance. Consequently, an arrangement of this kind limits the quality of the optical instrument in question or requires increased technical expenditure to improve the imaging characteristics through additional technical means.